This invention relates to a tape end detection apparatus which is used, for example, in a tape deck, to automatically stop or reverse the tape deck operation upon completion of the tape travel.
Usually, an electric tape-end detection apparatus detects the tape end in accordance with the presence or non-presence of a signal which is generated in response to the rotation of the tape reel. In this prior apparatus, there is provided a pulse generator which generates pulses responsive to the rotation of the supply reel or take-up reel and, when the pulse interval between the pulses from the pulse generator has exceeded a specified length of time, the power source of, for example, the deck is turned off. In this way, the automatic deck stopping operation based upon the detection of the tape end is performed after the lapse of a specified length of time from the stoppage of the reel rotation.
The automatic stopping operation time or auto-reverse time, i.e., the tape end detection time, preferably, is short. When, however, such tape end detection time is set at too short a time, some inconvenience will occur, for example, at a time when the tape is slackened. For instance, when the tape deck provided with the above-mentioned pulse generator on its take-up reel side is changed over to a rewind mode, even if tape remains to exist on the take-up reel side, the take-up reel is prevented from starting to rotate until said slackened portion of the tape is restored to the normal stretched or tensioned condition. Accordingly, if the period which is required for said tape slack to be corrected to permit the take-up reel to rotate to cause said pulse generator to generate a pulse is longer than said specified length of time, the deck operation automatically stops although a tape end is not reached. For these reasons, a limit is unavoidable for shortening the tape end detection time. The causes which prevent the shortening of such tape end detection time include said slackening of the tape, as well as a late rise in reel rotation speed due to based the inertia, etc. of a tape transport system.
Using typical numerical values, below is a discussion of how much time is required for the above-mentioned tape end detection. Let us consider a situation and case in which a pulse generator is provided on the take-up reel side, to generate one pulse per rotation of the reel and in which it is desired to detect the tape end by the pulse generator. In the case of a microcassette tape, the rotational period of the reel under the constant tape transport mode is approximately 7.5 sec. at maximum. This means that the above-mentioned length of time must be 7.5 seconds or more. When it is assumed from this that the time length is 7.5 seconds plus 0.5 sec. as an allowance, then said tape end detection time should be at least 8 seconds. This time length of 8 seconds is too long to be practical.
When, on the other hand, use is made of a pulse generator which generates, for example, 8 pulses per one rotation of the take-up reel, said tape end detection time becomes (7.5/8)+0.5.perspectiveto.1.5 seconds. This time length would raise no practical inconvenience. However, when the tape end detection time is shortened as such, if there occurs a delay in the start of the tape transport system due to the inertia of the capstan-flywheel or a slackening in the tape condition, such delay or slackening may cause an automatic stop of the tape transport at a tape position which is not the end. This means that the tape end detection apparatus makes an erroneous operation.